The basis for the realization of high-speed engines is a shorter piston stroke, but the shortening of the piston stroke will lead to a series of problems, such as insufficient low-torque, insufficient mixture combustion, etc., so it is generally more difficult to design a high-speed engine, and the cost Also higher. Then why do some manufacturers spare no effort to develop this type of engine? In fact, the reason is very simple, mainly to increase the output horsepower. There are generally several ways to obtain higher horsepower output: increase displacement, increase speed, and supercharge.
The first is to increase the displacement. Although this method is simple and rude, the effect is good, and it has been popular with American brands in the past. It can be said that if the fuel consumption and emissions are not considered, this is a very good engine power solution, but the standards of emissions and fuel consumption in countries around the world are becoming more and more perverted. How can these factors not be considered?
The second is to increase the engine speed. On the premise of not increasing the volume and weight of the engine, by increasing the speed, the number of work done by the piston per unit time increases, thereby increasing the maximum horsepower.
In fact, this also explains why high-revving engines are often used in racing cars. After all, the competition has rules, the displacement is limited, and the air intake density cannot be improved (some events require only natural air intake). To make the car run faster, you can only work on the frequency of work per unit time.
When we come to the civilian field, we will also see some high-revving engines, such as the Honda K20A, which is regarded as a “magic machine” by fans. The K20A is a four-cylinder naturally aspirated engine that Honda mainly promoted after entering the 21st century. The legend of the Integra Type-R model has made the engine’s status. It can be said that the K20A is another demonstration of Honda’s strength in order to prove to the world that it has car manufacturing capabilities. Like me, all readers are also obsessed with the high-revving engine because of the high-pitched voice after the VTEC is turned on. Yes, in Honda really brought us such a touch in those days. However, in fact, not all high-revving engines are out of reach. Everyone is familiar with the “old three” (Jetta, Santana, Beverly) in the past, and Beverly’s engines have relatively obvious high-revving tendency.
From the above text, you have probably already understood the reason why high-rev engines have always been respected by car fans. Under the same output horsepower, it has a more compact size and lighter weight than large-displacement engines, which is suitable for civilian use. A performance car or a racing car is a huge advantage. In addition, because of the short piston stroke, the high-revving engine is more responsive to the throttle than the low-revving engine, so there is a big difference in the handling feel obtained. . As for whether the sound of passion is good or not, this is a subjective thing. After all, there are still many people who prefer the richness of large-displacement engines.
After feeling the advantages of the high-revving engine, we turn our attention back to the K20A. In the first decade of the 21st century, the K20A has undergone three evolutions, and in each stage, Honda has added more or less new technology to it. In fact, the K20A is still not perfect until today. Like many high-speed engines, it has to face or has faced the following shortcomings:
1) It is difficult to balance the cylinder well. If the cylinders of the engine are not precisely parallel, the high-speed movement of the piston will easily cause the vibration of the cylinder block. This may not be a big deal on a low-speed engine, but once the speed reaches 6000rpm or more, it may affect the balance of the engine. The key factor. For this reason, the manufacture of high-speed engines puts forward very high requirements on the machining accuracy of components, especially the cylinder and many moving parts need to be precisely measured.
2) The dynamic response is weak in the low speed range. The setting of the cylinder diameter larger than the stroke in the high-speed engine is theoretically difficult to bring about satisfactory low-torque performance. In order to better meet the daily use, civilian-grade high-speed engines inevitably have to be compensated by other technical means. This is insufficient. The Honda K20A is derived from the F20C engine mounted on the S2000. Compared with the latter, the VTEC variable valve timing technology it adds makes the valve rhythm more flexible, and the cylinder adopts a relatively moderate 86mm X 86mm (bore diameter X stroke). The design is to improve the problem of weak low-rotation power on the F20C.
3) Easy to knock. The compression ratio of high-speed engines is generally high, and poor control can easily lead to abnormal combustion in the cylinder. Therefore, the 4-2-1 exhaust used in the racing field in the past has also been fed back to the civilian model. It can reduce the exhaust interference between the various cylinders, better control the combustion chamber temperature, and also help the intake air. Take in more air during the stroke.
4) Easy to channel gas. Ordinary internal combustion engines still have this problem, and of course high-rev engines are even more so. In the past, in order to solve similar problems on the K20A, Honda used a larger oil filter in addition to the crankcase ventilation system, in order to purify the oil as much as possible.
5) Great wear and tear. The high-speed reciprocating motion of the piston and the cylinder will inevitably cause serious wear to the components. At this time, the lubrication system is mentioned in a very prominent position. The oil with lower viscosity is theoretically more suitable for high-speed engines. The matching gap between them puts forward very high requirements.
6) High cost. Adding so many new technologies and processes, the cost is not high, and this is the reason why many civilian brands do not play with high-revving engines, because even if a product meets the expected requirements in all aspects, it may still be sold because of sales. Overpriced and eliminated from the market. Supercars are different. These luxury goods that sell for millions at every turn can make up for the high expenditure on development through various premiums, and in the end, they can even get a lot of profit from the high-speed selling point.
To be honest, now an ordinary 1.4L turbocharged engine can easily reach the maximum horsepower of 150 hp, and the 2.0L self-priming high-speed engine developed after a long time of waste is only the same, and the latter is more cruel. The cost is much higher than the former. Seeing this, it is estimated that you will also feel that playing with a high-revving engine is a thankless business. Although you have used all kinds of good things, the result is not as rough as a turbo.
Of course, our love for high-rev engines has nothing to do with these data, but more about the special pleasures it brings us that are different from ordinary engines, which may be the measurements made by engineers every time for accuracy, or after VTEC is turned on. High-pitched voice.
